Fantastic! I've been looking high and low for this information.
I originally had been hoping that the worker thread would provision *both* the public and personal free busy items. This would have been a great workaround to the problems I'm facing trying to find an alternative for provisioning both these items by manipulating Outlook using the object model to create them as a side-effect of posting a dummy appointment (although I found out I didn't have to save the appointment).
Alas it turned out to only provision the public free/busy and not the local which is required for doing the delegation and flipping the resource scheduling bits required for creating conference rooms (Why the hell are these on the LocalFreebusy?!?).
Unfortunately using the object model has turned out to be completely unreliable. Particularly it's conflicts with CDOEX.
So I've dived into the ol' Outlook Spy to figure out what I need to do to simulate the Outlook app (the key bit I missed earlier was the PR_FREEBUSY_ENTRYIDS prop on the Inbox and Root folder).
Any warnings from the wise before going completely down this hole? (local free/busy item provisioning)